Wet-chemical processes play an important role in the manufacture of electronic components, both in the removal (etching) and in the deposition of materials (plating). When semiconductor devices (ICs and LSIs) are mounted on a circuit, the bond pads of the semiconductor devices are provided with projecting metal contacts (so-called bumps), after which these bumps are connected to the circuit by bonding, welding, soldering or thermocompression (so-called flip chip principle). By TAB (tape automated bonding) ICs can be provided on a flexible tape comprising circuits.
Such a method is known from European Patent Application EP-A 308971. A semiconductor device comprising aluminium bond pads is first subjected to an activation treatment with an aqueous palladium-salt solution and then provided with nickel bumps. For this purpose, an electroless nickel bath is used.
Such electroless metallization processes are, in principle, isotropic, i.e. the deposition rate of the metal is equal in all directions. In the case of substrates comprising a thin coating layer in which apertures are formed which define the bond pads and which are to be metallized, lateral overgrowth of the coating layer takes place in the metallization process as soon as the metal layer has completely filled the aperture in the coating layer. In the case of semiconductor devices, the coating layer (also termed passivating layer) consists mostly of SiO.sub.2 or Si.sub.3 N.sub.4. The metal bumps project from the coating layer and, as a result of lateral overgrowth, partly cover the coating layer. As a result of the increasing miniaturization the risk of a short-circuit between adjacent bumps increases.